Internal combustion engines are known that include a plurality of cylinders with at least one of the plurality of cylinders being dedicated to exclusively providing exhaust gas recirculation to the intake manifold. Also referred to as dedicated EGR engines, such configurations can be used with fuels of all types, including natural gas, gasoline, and diesel fuel.
Spark-ignition engines typically operate by introducing a stoichiometric mixture of air and fuel into a cylinder of the engine. A piston then compresses this mixture, and at a predetermined crankshaft angle, a spark plug will ignite the air/fuel mixture producing a flame front that propagates through the combustion chamber. The rapid increase in heat from the burned fuel triggers an increase in pressure which forces the piston downward in the cylinder. The exhaust gases from the combustion event are expelled from the cylinder through the exhaust valve into an exhaust manifold.
Dedicated EGR engines have a split exhaust manifold in which the exhaust from the dedicated EGR cylinder is divided from the exhaust of the other cylinders. Under operating conditions that produce high exhaust pressures in the EGR manifold, internal residuals of the exhaust can remain in the dedicated EGR cylinder, and in some cases can be pushed back through the cylinder to the intake manifold, which increases the potential for knock occurrence and combustion instability.
Dedicated EGR engines can enjoy greatly simplified controls and pressure management, fewer hardware devices, and other benefits. However, these simplifications come at the cost of a loss of control over the system, including a loss of control due to the different conditions that may be present in the EGR cylinder(s) compared to the other cylinders. Therefore, operating the dedicated EGR cylinder(s) in the same manner as the other cylinders may not result in the desired outputs. As a result further technological developments are desirable in this area.